This invention relates to a remote copy method of transferring data on a block basis of a storage system between NAS systems.
In a storage system represented by a disk array, a storage area in a disk drive in the storage system is logically partitioned to be provided to a host computer as a volume. The storage system is connected to a network, and the host computer connects to the storage system through the network to use the volume. There is known a network attached storage (NAS) system as an example of the storage system for providing a volume through a network as described above. In the NAS system, an operating system or a file system operates to execute a file I/O in response to a request from a NAS client (host computer) with respect to files stored in each volume.
As regards the NAS system described above, there has been disclosed a method of conducting remote copy between NAS systems by using data in an updated block of a volume storing files and differential data between snapshots of the volume (JP 2005-292952 A).
Also, there has been disclosed a method used for conducting remote copy between NAS systems, in which contents of update of a file in a source NAS system and a management information record of the file are received by a destination NAS system and stored in a volume, and the destination NAS system updates management information of the file stored in a cache memory with reference to the management information record of the file which has been stored in the volume (JP 2005-128861 A). According to this conventional example, when data is updated at a local site, contents of the update are copied in real time to a file system at a remote site, to thereby make latest file data available for reference.